N-body simulations, weak lensing, and photo-z\u27s: Numerical projects in cosmology

General Relativity is an extremely well-tested theory over 15 orders of magnitude, on laboratory to solar system scales. However, recent measurements, including evidence from Type Ia supernovae, show that the expansion of the universe is accelerating. This means that GR, cannot unproblematically be extrapolated to fit the properties of our universe on horizon scales. With recourse to either a strange form of energy density ( dark energy ), or a modification of GR, the acceleration can be explained; distinguishing which is the correct model requires detailed observations of large-scale structure formation. In this thesis, I address three issues that are important to these observations: generating predictions by N-body simulation of alternate gravity models, efficiently obtaining accurate redshifts for galaxies using photometric redshifts with surface brightness priors, and finally modeling PSF effects for a proposed weak lensing survey